I have serial #'s off my drive it should be a xz thats what the guy told me when I bought my boat numbers are om137518. Is the prop shaft the same size on a bravo 1 as the xz?? Thanx for any help you can give me!

Yes, it is the same as Bravo 1 , you should have a larger universal joint and the spanner nut should look like the XR, has holes around instead of the teeth.

no the prop shaft is NOT the same size as the bravo one. It is 1.25 inch shaft like the xr drive.

Mercury shows that serial as a Bravo 3 X, so what you actually have would depend on the lower that is installed.

See:
http://www.go-fast.com/mercruiser_bravo_sterndrives.htm

Thanx for all the help! I looked at the link you sent me and my drive has only one prop. Is a bravo 3x good?? I just put in 670hp n/a motor will tha drive hold up good?? Thanx

I would like to add that my boat is an 01' and my serial # starts with OM-114........02 couldnt have been the first yr for the beefed up B1.